67 research outputs found
Variations of flaring kernel sizes in various parts of the H-alpha line profile
We analyze the temporal variations of the sizes and emission intensities of
thirtyone flaring kernels in various parts of the H{\alpha} line profile. We
have found that the areas of all kernels decrease systematically when observed
in consecutive wavelengths toward the wings of the H{\alpha} line, but their
areas and emission intensity vary in time. Our results are in agreement with
the commonly accepted model of the glass-shaped lower parts of the magnetic
flaring loops channelling high energy variable particle beams toward the
chromospheric plasma. High time resolution spectral-imaging data used in our
work were collected using the Large Coronagraph and Horizontal Telescope
equipped with the Multi-channel Subtractive Double Pass Spectrograph and the
Solar Eclipse Coronal Imaging System (MSDP-SECIS) at the Bia{\l}k\'ow
Observatory of the University of Wroc{\l}aw, Poland
Sizes of flaring kernels in various parts of the H-alpha line profile
In this paper we present new results of spectraphotometrical investigations
of the flaring kernels sizes and their intensities measured simultaneously in
various parts of the H-alpha line profile. Our investigations were based on the
very high temporal resolution spectral-imaging observations of the solar flares
collected with Large Coronagraph (LC), Multi-channel Subtractive Double Pass
Spectrograph and Solar Eclipse Coronal Imaging System (MSDP-SECIS) at Bialkow
Observatory (University of Wroclaw, Poland). We have found that the areas of
the investigated individual flaring kernels vary in time and in wavelengths as
well as the intensities and areas of the H-alpha flaring kernels decreased
systematically when observed in consecutive wavelengths toward the wings of the
H-alpha line. Our result could be explained as an effect of the cone-shaped
lower parts of the magnetic loops channeling high energy particle beams
exciting chromospheric plasma.Comment: Paper accepted to print in Annales Geophysicae (Special Issue: SOHO
20 Solar Conference); 6 pages, 7 figure
Plasma heating in the very early phase of solar flares
In this paper we analyze soft and hard X-ray emission of the 2002 September
20 M1.8 GOES class solar flare observed by RHESSI and GOES satellites. In this
flare event, soft X-ray emission precedes the onset of the main bulk hard X-ray
emission by ~5 min. This suggests that an additional heating mechanism may be
at work at the early beginning of the flare. However RHESSI spectra indicate
presence of the non-thermal electrons also before impulsive phase. So, we
assumed that a dominant energy transport mechanism during rise phase of solar
flares is electron beam-driven evaporation. We used non-thermal electron beams
derived from RHESSI spectra as the heating source in a hydrodynamic model of
the analyzed flare. We showed that energy delivered by non-thermal electron
beams is sufficient to heat the flare loop to temperatures in which it emits
soft X-ray closely following the GOES 1-8 A light-curve. We also analyze the
number of non-thermal electrons, the low energy cut-off, electron spectral
indices and the changes of these parameters with time.Comment: Comments: 17 pages, 5 figures, The Astrophysical Journal Letters
(accepted, October 2009
Search for Rapid Changes in the Visible-Light Corona during the 21 June 2001 Total Solar Eclipse
Some 8000 images obtained with the SECIS fast-frame CCD camera instrument
located at Lusaka, Zambia, during the total eclipse of 21 June 2001 have been
analyzed to search for short-period oscillations in intensity that could be a
signature of solar coronal heating mechanisms by MHD wave dissipation. Images
were taken in white- light and Fe XIV green-line (5303 A) channels over 205
seconds (frame rate 39 s-1), approximately the length of eclipse totality at
this location, with a pixel size of four arcseconds square. The data are of
considerably better quality than were obtained during the 11 August 1999 total
eclipse, observed by us (Rudawy et al.: Astron. Astrophys. 416, 1179, 2004), in
that the images are much better exposed and enhancements in the drive system of
the heliostat used gave a much improved image stability. Classical Fourier and
wavelet techniques have been used to analyze the emission at 29518 locations,
of which 10714 had emission at reasonably high levels, searching for periodic
fluctuations with periods in the range 0.1-17 seconds (frequencies 0.06-10 Hz).
While a number of possible periodicities were apparent in the wavelet analysis,
none of the spatially and time-limited periodicities in the local brightness
curves was found to be physically important. This implies that the pervasive
Alfven wave-like phenomena (Tomczyk et al.: Science 317, 1192, 2007) using
polarimetric observations with the CoMP instrument do not give rise to
significant oscillatory intensity fluctuations.Comment: Accepted by Solar Physics; 16 figure
Determination of 3D Trajectories of Knots in Solar Prominences Using MSDP Data
In this paper we present a new method of restoration of the true
thee-dimensional trajectories of the prominence knots based on ground-based
observations taken with a single telescope, which is equipped with a
Multi-Channel Subtractive Double Pass imaging spectrograph. Our method allows
to evaluate true three-dimensional trajectories of the prominence knots without
any assumptions concerning the shape of the trajectories or dynamics of the
motion. The reconstructed trajectories of several knots observed in three
prominences are presented.Comment: 14 pages, 9 figures, accepted for publication in Solar Physic
Plasma heating in the very early and decay phases of solar flares
In this paper we analyze the energy budgets of two single-loop solar flares
under the assumption that non-thermal electrons are the only source of plasma
heating during all phases of both events. The flares were observed by the
Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and Geostationary
Operational Environmental Satellite (GOES) on September 20, 2002 and March 17,
2002, respectively. For both investigated flares we derived the energy fluxes
contained in non-thermal electron beams from the RHESSI observational data
constrained by observed GOES light-curves. We showed that energy delivered by
non-thermal electrons was fully sufficient to fulfil the energy budgets of the
plasma during the pre-heating and impulsive phases of both flares as well as
during the decay phase of one of them. We concluded that in the case of the
investigated flares there was no need to use any additional ad-hoc heating
mechanisms other than heating by non-thermal electrons.Comment: 22 pages, 10 figures, The Astrophysical Journal (accepted, March
2011
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